The present invention relates generally to magnetic coil construction and, more particularly, to a method of reducing partial discharge between adjacent conductive layers of the coil and increasing a bore radius and coil operating voltages.
Electromagnetic coils have applications across a wide spectrum of industry. Electromagnetic coils have applications in transportation systems such as maglev trains, electrical power systems in devices such as transformers, and medical imaging technologies such as magnetic resonance imagining or MRI systems. Construction of the coil is directly related to the ultimate application of the coil and directly effects operation of the coil and performance of the system which utilizes the coil.
In the medical imaging field, the construction of the coil is an important consideration to the construction and operation of the medical imaging device. The coil generally consists of a plurality of conductive plates adhered together and shaped to define a bore. During imaging of a patient, the patient is passed into the bore of the imaging device. Some patients are apprehensive about the relatively closed space of the bore of the coil. This apprehension can detrimentally affect patient physiology which in turn detrimentally affects image quality and/or integrity. Accordingly, it would be desirable to expand the area of the bore of the coil to minimize patient anxiety associated with the scanning process. Furthermore, increasing the size of the bore of the coil provides for imaging of subjects/parcels with larger cross-sectional areas.
The size of the bore opening can be increased without increasing the overall size of the imaging device by reducing the spacing between adjacent conductive plates of the coil. However, decreasing this interlayer spacing increases the partial discharge between adjacent layers of the coil. As explained further below, in magnetic resonance imaging applications, increased partial discharge between layers of the coil negatively affects image quality.
Another consideration is the coils ability to function at operating parameters which are continually increasing. Particularly in the imaging field, providing a device capable of generating stronger gradients and/or faster slew rates provides for increased imaging functionality and improved device throughput. In order to generate the stronger gradients and the faster slew rates, the conductive plates of the coil are subjected to ever increasing operating voltages. These increased voltages also affect the partial discharge between adjacent layers of the coil. As the spacing between adjacent plate's decreases and the plates are subjected to increased operating voltages, there is a greater probability of increased partial discharge between adjacent layers of the coil.
In magnetic resonance imaging applications, partial discharge between layers of the coil causes white pixels thereby affecting imaging quality. Increasing the bore size, thereby decreasing the interlayer spacing between adjacent layers of the coil, increases the probability of partial discharge between adjacent layers and thereby detrimentally affects image quality. Increasing the operating voltage of the coil also increases the partial discharge between adjacent layers thereby detrimentally affecting image quality. Understandably, increasing the bore size as well as the operational power range of the imaging device compounds the detrimental effects of partial discharge between plates of the coil and detracts from image quality.
It would therefore be desirable to have a system and method capable of providing a coil with an increased bore diameter and constructed to operate at elevated power levels without detrimentally affecting the partial discharge of the coil.